This invention relates to a magnetic disc recording system, and more particularly to apparatus for centering, mounting and rotatably driving a removable recording disc within such system.
In magnetic recording disc drives systems utilizing removable disc recording media, it is necessary to locate such removable media very accurately both vertically and radially with respect to the axis of rotation in order that the recording and playback transducers attached to the drive may repeatably track the data recorded upon the disc. This requirement is particularly acute with the pursuit of ever higher recording densities and thus narrower and more precisely located recording tracks upon each disc. Such recording densities now exceed 1,000 per inch of radius upon some of the newer rigid disc systems. The problem is also made more acute by the desirability of ready removability of such recording discs contained within cartridge housings so that the cartridges may be quickly interchanged, while still retaining the precise positioning necessary for the high densities.
Various approaches to such mounting and rotational driving of the disc have been attempted. Most commonly there have been used various modifications of a conical spindle upon the disc drive with a conical recess in the center of the disc hub, so that the mating engagement between the two conical surfaces serves to provide for the necessary location of the disc. With such mountings the necessary rotational drive may be provided either through the conical hub and spindle or through engagement between other portions of the hub and disc drive.
While such conical spindle and hub recess arrangements have proved satisfactory in systems utilizing lower recording densities, it has been found that even small particles of foreign matter on either the spindle or the conical recess, or even slight irregularities of wear cause mispositioning of the disc with respect to the spindle sufficient to preclude accurate recording at the new, higher recording track densities. Accordingly, it has been necessary to seek other centering and drive arrangements for satisfactory use with high density recording arrangements.